[Bug other/52754] New: [4.7 regression, miscompilation] indirect indexing broken with -fpredictive-commoning

["kretz at kde dot org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52754

             Bug #: 52754
           Summary: [4.7 regression, miscompilation] indirect indexing
                    broken with -fpredictive-commoning
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: kretz@kde.org


Created attachment 27022
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27022
testcase

The attached testcase is compiled to access the indexes array at bogus offsets.
If line 8 is removed and line 7 written as
    unsigned int indexes[8] = { 0, 1, 2, 3, 4, 5, 6, 7 };
the error disappears.

% /opt/gcc-4.7.0/bin/g++ -msse2 -v -O1 -fpredictive-commoning main.cpp
Using built-in specs.
COLLECT_GCC=/opt/gcc-4.7.0/bin/g++
COLLECT_LTO_WRAPPER=/opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ./configure --prefix=/opt/gcc-4.7.0 --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --enable-languages=c,c++,fortran
--with-gmp=/opt/gcc-4.7.0 --with-mpfr=/opt/gcc-4.7.0 --with-ppl=/opt/gcc-4.7.0
--with-cloog=/opt/gcc-4.7.0 --with-libelf=/opt/gcc-4.7.0
--with-mpc=/opt/gcc-4.7.0 --enable-lto
Thread model: posix
gcc version 4.7.0 (GCC)
COLLECT_GCC_OPTIONS='-msse2' '-v' '-O1' '-fpredictive-commoning'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/cc1plus -quiet -v
-imultiarch x86_64-linux-gnu -D_GNU_SOURCE main.cpp -quiet -dumpbase main.cpp
-msse2 -mtune=generic -march=x86-64 -auxbase main -O1 -version
-fpredictive-commoning -o /tmp/ccmv6Zx9.s
GNU C++ (GCC) version 4.7.0 (x86_64-linux-gnu)
        compiled by GNU C version 4.7.0, GMP version 5.0.4, MPFR version 3.1.0,
MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
ignoring nonexistent directory
"/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0

/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0/x86_64-linux-gnu

/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../include/c++/4.7.0/backward
 /opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/include
 /usr/local/include
 /opt/gcc-4.7.0/include
 /opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/include-fixed
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
GNU C++ (GCC) version 4.7.0 (x86_64-linux-gnu)
        compiled by GNU C version 4.7.0, GMP version 5.0.4, MPFR version 3.1.0,
MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 32eb1a24aeca8b97e0c59b4b063f668f
COLLECT_GCC_OPTIONS='-msse2' '-v' '-O1' '-fpredictive-commoning'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'

/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/bin/as
--64 -o /tmp/cca4x2R5.o /tmp/ccmv6Zx9.s
COMPILER_PATH=/opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/:/opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/:/opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/bin/
LIBRARY_PATH=/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../lib64/:/lib/x86_64-linux-gnu/:/lib/../lib64/:/usr/lib/x86_64-linux-gnu/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/lib/:/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-msse2' '-v' '-O1' '-fpredictive-commoning'
'-shared-libgcc' '-mtune=generic' '-march=x86-64'
 /opt/gcc-4.7.0/libexec/gcc/x86_64-linux-gnu/4.7.0/collect2 --eh-frame-hdr -m
elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2
/usr/lib/x86_64-linux-gnu/crt1.o /usr/lib/x86_64-linux-gnu/crti.o
/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/crtbegin.o
-L/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0
-L/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../lib64
-L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu
-L/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../../../x86_64-linux-gnu/lib
-L/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/../../.. /tmp/cca4x2R5.o
-lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc
/opt/gcc-4.7.0/lib/gcc/x86_64-linux-gnu/4.7.0/crtend.o
/usr/lib/x86_64-linux-gnu/crtn.o

% ./a.out
[1]    7716 bus error  ./a.out